Problem: $ { {-1} \times \left[\begin{array}{rrr}{2} & {0} & {1} \\ {-2} & {0} & {4}\end{array}\right] = {?} } $
To multiply a matrix by a number, multiply each item of the matrix by the number. ${\left[\begin{array}{rrr}{-1}\times{2} & {-1}\times{0} & {-1}\times{1} \\ {-1}\times{-2} & {-1}\times{0} & {-1}\times{4}\end{array}\right]}$ Now, simplify: ${\left[\begin{array}{rrr}{-2} & {0} & {-1} \\ {2} & {0} & {-4}\end{array}\right]}$